fix: preserve bitfield width during integer promotion

[swananan]

Unsigned 25–31-bit fields lost their declared width before integer promotion and were treated as unsigned 32-bit values. Comparing them with a DWARF int valued -1, or applying bitwise NOT, division, and remainder, could disagree with the native C program.

Retain the bitfield value width until promotion. Fields whose values fit in int promote to signed 32-bit integers; full-width unsigned fields retain unsigned semantics. The change is rebased onto current main and contains one commit touching three files.

Validation:

• Unit coverage for signed and unsigned widths 1, 24, 25, 31, and 32, including repeated promotion.
• Two e2e tests compare tracing results with native C results for 24/25/31/32-bit fields across ordered comparison, bitwise NOT, division, and remainder. Both fail with the old promotion implementation and pass after rebuilding the fix.
• cargo fmt --all and full workspace Clippy with CI warning settings passed.
• All 955 non-e2e unit, integration, and documentation tests passed locally after refreshing workspace build inputs. Their test-name list exactly matches the successful GitHub Test Suite run.
• Full standard e2e passed: 347 tests, including both new regressions, 49 Rust script tests, and all 18 scalar-type tests.
• All 10 GitHub checks passed on 543e64d, including Standard E2E (347 tests), three full container topologies, host-PID smoke, and the DWARF performance check. The Standard E2E log confirms both new regressions ran and the Rust globals fixture was rebuilt with Rust 1.98.
• Local container-topology runs were omitted because this change does not touch container behavior; those topologies passed in GitHub CI.